JP2019035109A - Growing device and method of boron nitride film - Google Patents

Abstract

To form a uniform h-BN film more simply by using a horizontal type CVD device.SOLUTION: A growing device of a boron nitride film includes a horizontal type (lateral type) reaction tube 101 having one end provided with an introduction port 102 for introducing raw material gas, and the other end provided with a discharge port 103, a raw material gas supply part 104 for supplying the raw material gas into the reaction tube 101 from the introduction port 102, and an auxiliary reaction tube 105 arranged inside the reaction tube 101. The auxiliary reaction tube 105 is arranged extendedly in the same direction as an extension direction of the reaction tube 101, and the auxiliary reaction tube 105 includes a closed part 106 on the introduction port 102 side, and an opening 107 on the discharge port 103 side.SELECTED DRAWING: Figure 1

Description

  The present invention relates to a boron nitride film growth apparatus and method for forming a film made of hexagonal boron nitride.

  Hexagonal boron nitride (h-BN) is essentially an insulator, chemically inert, and has a smooth surface at the atomic level without dangling bonds, so graphene and other 2 Like the dimensional material, it is an excellent dielectric material for the device. For this reason, the manufacture of the h-BN film is a very important technique.

  Currently, as a technique for forming an h-BN film in a large area, there is a thermal CVD (Chemical Vapor Deposition) method that can be applied mainly to industries. For example, a thermal CVD method using a horizontal (horizontal) CVD apparatus can easily form a large-area h-BN film. However, in the formation of the h-BN film by such a CVD method, the uniformity of the film thickness (number of layers) is poor, and the characteristics are worse than those of the h-BN film manufactured by the peeling method. For example, amorphous particles may be formed. Further, even if a single layer of boron nitride is to be formed, a multilayer boron nitride layer or the like is formed. Such a three-dimensional structure has a problem of inducing a dielectric constant distribution in the thickness direction of the thin film (see Non-Patent Documents 1, 2, and 3).

  On the other hand, as a more homogeneous (high quality) h-BN formation technique, a technique for forming an h-BN film by epitaxial growth on Ir (111) by chemical vapor deposition of borazine (cyclotriborazane) ( Non-patent document 4). There is also a technique for growing an h-BN film on re-solidified Cu (see Non-Patent Document 5). In addition, there is a technique for synthesizing single crystal h-BN particles on a Cu-Ni alloy foil (Non-Patent Document 6). In addition, there is a technique for forming an h-BN single layer film in a region surrounded by a folded copper foil (Non-patent Document 7). There is also a technique of forming an h-BN film on a sapphire substrate at a very high temperature (Non-patent Document 8).

K. K. Kim et al., "Synthesis of Monolayer Hexagonal Boron Nitride on Cu Foil Using Chemical Vapor Deposition", Nano Letter, vol. 12, pp. 161-166, 2012. M. S. Bresnehan et al., "Integration of Hexagonal Boron Nitride with Quasi-freestanding Epitaxial Graphene: Toward Wafer-Scale, High-Performance Devices", ACS Nano, vol. 6, no. 6, pp. 5234-5241, 2012. C. Pan et al., "Coexistence of Grain-Boundaries-Assisted Bipolar and Threshold Resistive Switching in Multilayer Hexagonal Boron Nitride", Advanced Functional Materials, vol. 27, 1604811, 2017. F. Orlando et al., "Epitaxial Growth of a Single-Domain Hexagonal Boron Nitride Monolayer", ACS Nano, vol. 8, no. 12, pp. 12063-12070, 2014. R. Y. Tay et al., "Synthesis of aligned symmetrical multifaceted monolayer hexagonal boron nitride single crystals on resolidified copper", Nanoscale, vol. 8, pp. 2434-2444, 2016. G. Lu et al., "Synthesis of large single-crystal hexagonal boron nitride grains on Cu. Ni alloy", Nature Communications, vol. 6, 6160, 2015. X. Song et al., "Chemical vapor deposition growth of large-scale hexagonal boron nitride with controllable orientation", Nano Research, vol. 8, no. 10, pp. 3164-3176, 2015. A- R. Jang et al., "Wafer-Scale and Wrinkle-Free Epitaxial Growth of Single-Orientated Multilayer Hexagonal Boron Nitride on Sapphire", Nano Letters, vol. 16, pp. 3360-3366, 2016.

  However, the above-described conventional technology can form high-quality h-BN, but requires a specially designed substrate and requires a lot of energy and time, such as a significantly high temperature. There were problems such as rising costs. Thus, conventionally, there has been a problem that it takes time and cost to form uniform h-BN.

  The present invention has been made to solve the above-described problems, and an object thereof is to make it possible to more easily form a uniform h-BN film using a horizontal CVD apparatus.

  A boron nitride film growth apparatus according to the present invention includes a horizontal reaction tube, an introduction port for introducing a raw material gas provided on one side of the reaction tube, an exhaust port provided on the other side of the reaction tube, and an introduction port. A raw material gas supply unit for supplying a raw material gas to the reaction tube; and an inner portion of the reaction tube extending in the same direction as the extending direction of the reaction tube, the inlet side being closed and the outlet side being closed A sub-reaction tube having an opening, a substrate placing table on which a substrate to be processed is placed, and a heating unit for heating the inside of the reaction tube.

  In the boron nitride film growth apparatus, in the extending direction of the reaction tube, the position of the end portion on the discharge port side of the heating region by the heating unit is the same position as the opening of the secondary reaction tube.

  In the boron nitride film growth apparatus, the substrate mounting table may be disposed in a range of 130 mm to 230 mm inside the opening.

  In the boron nitride film growth apparatus, the substrate mounting table is preferably arranged so that the plane of the substrate is parallel to the extending direction of the reaction tube.

  A method of growing a boron nitride film according to the present invention is a method of growing a boron nitride film using the above-described boron nitride film growth apparatus, and comprises a catalytic metal serving as a catalyst for the growth of boron nitride on a substrate mounting table. A first step of placing the constructed growth substrate, a second step of heating the growth substrate by heating the inside of the reaction tube by a heating unit, a third step of supplying a source gas from the inlet, and an introduction And a fourth step of growing a boron nitride film made of hexagonal boron nitride on the heated growth substrate in a state where the source gas supplied from the mouth is flowing toward the outlet.

  As described above, according to the present invention, the horizontal reaction tube is provided with the sub-reaction tube whose inlet side is closed, so that it can be more easily and uniformly formed using the horizontal CVD apparatus. An excellent effect that an h-BN film can be formed is obtained.

FIG. 1 is a configuration diagram showing a configuration of a boron nitride film growth apparatus according to an embodiment of the present invention. FIG. 2 is a flowchart for explaining a method of growing a boron nitride film in the embodiment of the present invention. FIG. 3 is a photograph showing the results of observing the boron nitride film with a scanning electron microscope.

  A boron nitride film growth apparatus according to an embodiment of the present invention will be described below with reference to FIG. FIG. 1 schematically shows a cross section. This boron nitride film growth apparatus includes a horizontal (horizontal) reaction tube 101 first. The reaction tube 101 is used in a general horizontal CVD apparatus. For example, the reaction tube 101 is a cylinder, provided with an introduction port 102 for introducing a source gas at one end and an exhaust port 103 at the other end. Yes.

The growth apparatus further includes a source gas supply unit 104 that supplies source gas to the reaction tube 101 from the inlet 102. The source gas is, for example, ammonia borane (borazane, H ₃ NBH ₃ ) gas. The source gas supply unit 104 supplies source gas together with a carrier gas such as hydrogen, for example.

  In addition, this growth apparatus includes a secondary reaction tube 105 inside the reaction tube 101. The sub-reaction tube 105 extends in the same direction as the reaction tube 101 extends. Further, the side reaction tube 105 is closed at a portion 106 on the introduction port 102 side, and includes an opening 107 on the discharge port 103 side. The secondary reaction tube 105 may be made of a material that is stable at a high temperature of 1000 ° C. or higher, such as quartz, sapphire, alumina, or tungsten. In addition, a substrate mounting table 108 on which a growth substrate 121 to be processed is mounted is provided inside the reaction tube 101. For example, the substrate mounting table 108 arranges the plane of the growth substrate 121 in parallel with the extending direction of the reaction tube 101.

  The growth apparatus also includes a heater (heating unit) 109 that heats the inside of the reaction tube 101, as in a general horizontal CVD apparatus. Here, in the extending direction of the reaction tube 101, the position of the end 109 a on the discharge port 103 side of the heating region by the heater 109 is the same position as the opening 107 of the sub reaction tube 105.

  Here, the reaction tube 101 is a cylinder having a diameter of 36 mm. In addition, the heater 109 includes a heating region extending in a length of 490 mm in the extending direction of the reaction tube 101. The side reaction tube 105 is a cylinder having a diameter of 16 mm and has a length of 300 mm in the extending direction of the reaction tube 101. Note that the length of the reaction tube 101 may be the same as or shorter than the heating region by the heater 109.

  Next, a method for growing a boron nitride film in the embodiment of the present invention will be described with reference to FIG. This growth method uses the growth apparatus described above. First, in the first step S <b> 101, the growth substrate 121 is mounted on the substrate mounting table 108. The growth substrate 121 is made of a catalyst metal that serves as a catalyst for the growth of boron nitride, such as copper or nickel. For example, the growth substrate 121 may be a copper foil.

  Next, in the second step S102, the growth substrate 121 is heated by heating the inside of the reaction tube 101 with the heater 109. For example, the growth substrate 121 is heated to about 1000 ° C.

  Next, in the third step S <b> 103, the source gas supply unit 104 is operated to supply source gas from the inlet 102. For example, ammonia borane may be heated to 70 to 90 ° C. to generate ammonia borane gas as a source gas, hydrogen gas as carrier gas, and the generated ammonia borane gas to be supplied. The source gas supplied in this manner flows through the reaction tube 101 from the inlet 102 to the outlet 103. However, the portion 106 of the side reaction tube 105 is closed. For this reason, the raw material gas moves to the side surface of the growth substrate 121 from the opening 107 side mainly by the action of diffusion (mass transfer).

  Next, in the fourth step S <b> 104, as described above, the source substrate gas supplied from the inlet 102 flows through the reaction tube 101 toward the outlet 103, and the growth substrate 121 that is heated is heated. A boron nitride film made of hexagonal boron nitride is grown thereon. In the above description, the source gas is supplied onto the growth substrate 121 heated to a predetermined temperature. However, the present invention is not limited to this. As described above, the source gas may be supplied onto the growth substrate 121, and heating of the growth substrate 121 may be started in this state.

  Hereinafter, experimental results of actually producing a boron nitride film by the boron nitride film growth method using the boron nitride film growth apparatus according to the embodiment will be described. In the experiment, a reference h-BN (comparative sample) was also produced with a general horizontal CVD apparatus.

  In the experiment, the sample 1 was prepared by arranging the growth substrate 121 in the sub-reaction tube 105 within a range of 235 mm or more inside the opening 107. In addition, the sample 2 was prepared by arranging the growth substrate 121 inside the sub-reaction tube 105 in a range of 175 mm to 230 mm away from the opening 107. In addition, in the sub reaction tube 105, the growth substrate 121 was arranged in a range away from 130 mm to 170 mm inside the opening 107 to prepare the sample 3. In addition, the sample 4 was prepared by arranging the growth substrate 121 in a range 90 mm away from the opening 107 inside the side reaction tube 105. In the experiment, the growth substrate 121 was directly placed inside the sub reaction tube 105 without using the substrate placing table 108.

In any sample preparation, hydrogen is supplied at 20 to 40 sccm as a carrier gas. Note that sccm is a unit of flow rate, and indicates that a fluid at 0 ° C. and 1013 hPa flows 1 cm ³ per minute. Further, in the source gas supply unit 104, ammonia borane was heated to 70 to 90 ° C. to generate ammonia borane gas and supplied as source gas. The growth temperature was set to 1000 to 1050 ° C. by heating the heater 109.

  The results of observation (photographing) of each sample described above with a scanning electron microscope will be described with reference to FIG. In FIG. 3, (a) shows the result of the comparative sample, (b) shows the result of Sample 1, (c) shows the result of Sample 2, (d) shows the result of Sample 3, and (e ) Shows the result of Sample 4.

  As shown to (a) of FIG. 3, in the comparative sample, the single layer h-BN film | membrane which covers the whole surface contains many multi domains. In FIG. 3A, the white dot-shaped portion is a portion of the multilayer h-BN having a very small size. In FIG. 3A, the background contrast is due to copper grains having different plane orientations.

  In samples 1 to 4 shown in FIGS. 3B to 3E, the formation of multi-domains such as multilayer h-BN is considerably suppressed.

  Here, in FIG. 3B, the background contrast is due to copper grains having different plane orientations. In FIG. 3B, the white dot-shaped portion is a multilayer h-BN having a very small size. In FIG. 3B, the black dot-shaped portion is a single phase h-BN.

  In FIG. 3C, the black portions are connected single-phase h-BN domains, and the bright triangular portions are portions where copper is exposed. FIG. 3D shows a state in which the whole is covered with a single phase h-BN, and the background contrast is due to copper grains having different plane orientations. Further, FIG. 3E shows a state where the whole is covered with the single-phase h-BN, and a white dot-like portion is a multilayer h-BN formed on the single-phase h-BN. The background contrast is due to copper grains with different plane orientations.

  More specifically, the coverage of the single layer h-BN is related to the position of the growth substrate 121 from the opening 107 inside the secondary reaction tube 105, which is divided into four regions. First, there is a region where h-BN does not grow as shown in FIG. Second, there is a region where a uniform quasi-single layer h-BN film grows as shown in FIG. Third, there is a region where a single-layer h-BN film in a state of being completely and completely covered is grown. Fourth, there is a region in which the single layer h-BN is formed in a multilayer structure of several layers.

  The first region and the fourth region are out of the optimal arrangement range of the growth substrate 121 for the growth of the uniform single layer h-BN in the present apparatus. Therefore, the substrate mounting table 108 (growth substrate 121) may be disposed in the range of 130 mm to 230 mm inside the opening 107 of the sub reaction tube 105. In other words, the growth substrate 121 (the center position thereof) disposed inside the sub-reaction tube 105 only needs to be within a range of 130 mm to 230 mm from the opening 107.

  As described above, according to the present invention, the horizontal reaction tube is provided with the sub-reaction tube whose inlet side is closed, so that it can be more easily and uniformly formed using the horizontal CVD apparatus. An h-BN film can be formed.

  The present invention is not limited to the embodiment described above, and many modifications and combinations can be implemented by those having ordinary knowledge in the art within the technical idea of the present invention. It is obvious. For example, in the above description, ammonia borane gas is used as the source gas, but the present invention is not limited to this. For example, triethylboron and ammonia gas may be used as the source gas.

  DESCRIPTION OF SYMBOLS 101 ... Reaction tube, 102 ... Inlet port, 103 ... Discharge port, 104 ... Raw material gas supply part, 105 ... Sub reaction tube, 106 ... Part, 107 ... Opening part, 108 ... Substrate mounting table, 109 ... Heater (heating part) 109a ... end portions, 121 ... growth substrate.

Claims (5)

A horizontal reaction tube,
An inlet for introducing a raw material gas provided at one end of the reaction tube;
A discharge port provided at the other end of the reaction tube;
A source gas supply unit for supplying source gas to the reaction tube from the inlet;
A sub-reaction tube that is disposed in the reaction tube in the same direction as the reaction tube and is closed on the inlet side and has an opening on the discharge side;
A substrate platform on which a substrate to be treated is placed and placed inside the reaction tube;
And a heating unit that heats the inside of the reaction tube. The boron nitride film growth apparatus according to claim 1,
In the extending direction of the reaction tube, the position of the end portion on the discharge port side of the heating region by the heating unit is the same position as the opening of the sub-reaction tube. Growth equipment. The boron nitride film growth apparatus according to claim 1 or 2,
The substrate mounting table is arranged in a range of 130 mm to 230 mm inside the opening. The boron nitride film growth apparatus. In the growth apparatus of the boron nitride film of any one of Claims 1-3,
The substrate mounting table is configured to arrange a plane of the substrate parallel to the extending direction of the reaction tube. A method for growing a boron nitride film using the boron nitride film growth apparatus according to any one of claims 1 to 4,
A first step of placing a growth substrate composed of a catalytic metal serving as a catalyst for the growth of boron nitride on the substrate placement table;
A second step of heating the growth substrate by heating the inside of the reaction tube by the heating unit;
A third step of supplying a source gas from the inlet;
A fourth step of growing a boron nitride film made of hexagonal boron nitride on the heated growth substrate in a state where the source gas supplied from the introduction port flows toward the discharge port; A method of growing a boron nitride film, comprising: